Truss foundations for frost-heave environments

Abstract

A truss foundation for single-axis trackers that are installed in climates that experience significant frost heave. In some cases, truss legs are oriented plumb, to eliminate adfreeze moment on below-ground components in the frost zone. Different truss caps may be used depending on the type of single-axis tracker and/or tracker component is supported. In some cases, truss legs may curve just before entering the ground. In others, below-ground and above-ground components may extend along the same axis and remain plump with the truss cap providing additional elevation to for the tracker to clear the wider truss legs.

The invention claimed is: 
     
         1 . A truss foundation for a single-axis tracker comprising:
 a pair of truss legs extending into underlying ground; and   a truss cap interconnecting the pair of truss legs, wherein the truss cap provides an elevated mounting surface for a tracker component and includes a pair of connecting portions angled apart from one another that extend below the elevated mounting surface that set a substantially fixed leg separation angle between the truss legs and are received in respective ones of the truss legs, each truss leg comprising an upper leg portion sleeved over a coupler attached to an upper end of a driven screw anchor extending at a substantially plumb orientation below a seasonally expansive layer of the underlying ground.   
     
     
         2 . The truss foundation according to  claim 1 , wherein the tracker component is selected from the group consisting of a tracker bearing, a tracker drive motor, and a tracker center structure assembly. 
     
     
         3 . The truss foundation according to  claim 1 , wherein connections between the upper leg portions and the screw anchors and between the upper leg portions and the truss cap are crimp connections made without fasteners. 
     
     
         4 . The truss foundation according to  claim 1 , wherein each upper leg portion is oriented at an angle with respect to plumb. 
     
     
         5 . A truss foundation for supporting a single-axis tracker above underlying ground comprising:
 a pair of adjacent truss legs; and   a truss cap joining above-ground ends of the pair of adjacent truss legs, wherein the truss cap comprises a pair of connecting portions angled apart from one another that set a substantially fixed leg separation angle between the truss legs and are received in respective ones of the truss legs, each truss leg comprising an upper leg portion sleeved over and connected to a coupler of a driven screw anchor, wherein the screw anchor is driven at a substantially plumb orientation.   
     
     
         6 . The truss foundation according to  claim 5 , wherein each truss leg extends away from the truss cap at an angle with respect to plumb and terminates in an elbow that couples to a substantially plumb driven screw anchor. 
     
     
         7 . The truss foundation according to  claim 5 , wherein each substantially plumb driven screw anchor extends below a seasonally expansive layer of the underlying ground. 
     
     
         8 . The truss foundation according to  claim 5 , wherein the truss cap comprises a mounting portion for supporting a tracker component. 
     
     
         9 . The truss foundation according to  claim 8 , wherein the tracker component is selected from the group consisting of a bearing assembly, a drive motor, and a center structure. 
     
     
         10 . The truss foundation according to  claim 5 , wherein the truss cap comprises a single upper support portion for supporting a tracker component. 
     
     
         11 . The truss foundation according to  claim 5 , wherein the truss cap comprises a pair of upper support portions for supporting a tracker component. 
     
     
         12 . An assembly comprising:
 a pair of truss legs extending into underlying ground; and   a truss cap interconnecting the pair of truss legs, wherein the truss cap provides at least one elevated mounting surface for a tracker component and includes a pair of connecting portions angled apart from one another that extend below the at least one elevated mounting surface and that set a substantially fixed leg separation angle and are received in respective ones of the truss legs, each truss leg comprising an upper leg portion sleeved over and connected to a coupler of a driven screw anchor, wherein the screw anchor is driven at a substantially plumb orientation.   
     
     
         13 . The assembly according to  claim 12 , wherein the connecting portions and upper leg portions are at an angle with respect to plumb. 
     
     
         14 . The assembly according to  claim 12 , further comprising a tracker component attached to the at least one elevated mounting surface. 
     
     
         15 . The assembly according to  claim 14 , wherein the tracker component comprises a component selected from the group consisting of a bearing assembly, a drive motor, and a center structure.